1. Field of the Invention
The present invention relates to a semiconductor device and, more particularly, to a semiconductor device and a method for manufacturing the same, in which a strained silicon layer functions as an active layer, and an insulating layer is formed in or under the strained silicon layer under source/drain regions, thereby improving the operational characteristics of the semiconductor device.
2. Discussion of the Related Art
Generally, when germanium (Ge) is put or deposited onto a silicon (Si) substrate, a germanium layer may be formed on the silicon substrate at a predetermined temperature. Then, a silicon layer may be formed on the germanium layer, so that a strained silicon layer is formed having a distance between certain locations in the Si lattice, such that the deposited Si lattice is substantially identical to that of the germanium layer. Accordingly, in this strained silicon layer, a lattice structure may contain greater distances between silicon atoms in the lattice.
With the trend toward miniaturization of semiconductor devices, conventional Si structures can have a problem relating to a decrease in the mobility of electrons and holes. In order to address this mobility problem, strained silicon may be used for a substrate of the semiconductor device.
Where a strained silicon substrate is used, it is possible to increase the mobility of electrons and holes, thereby improving the operational characteristics of the semiconductor devices thereon. However, such semiconductor devices have also been minimized to the nano-size range, whereby problems such as leakage current, drain induced barrier lowing (DIBL), and junction breakdown voltage may arise.